1. Field of the Invention
This invention is concerned with the resolution of water-bituminous emulsions and conventional petroleum emulsions by treatment with polyethylene oxide resins of optimum molecular weight at a controlled pH range. The invention is also concerned with the separation of water from bitumen which has been brought to the surface in the form of water-in-oil or oil-in-water emulsions by an in situ recovery process.
2. STATEMENT OF THE PRIOR ART
Numerous hot water extraction methods exist for separating crude oil from bituminous sands (tar sands, oil sands and the like) which involve mixing such sands with hot or cold water and separating the sand from the resulting emulsions.
The technical difficulty encountered with emulsions produced by an situ operations is that the liquid mixture is a highly stabilized emulsion which is difficult to break with standard treating chemicals.
The attempts made in the prior art to break emulsions resulting from hot water extraction processes are represented, inter alia, by the techniques described in U.S. Pat. Nos. 3,808,120; 3,607,721, and 3,487,003.
U.S. Pat. No. 3,808,120 describes a method for separating at least water and solids from the froth produced in a hot water process for separating bitumen from tar sands by treating the froth in at least one cyclone zone after which it is treated in at least two centrifuging zones.
In U.S. Pat. No. 3,606,721, a process for the removal of solids and emulsified water from a bituminous emulsion is disclosed which comprises diluting the emulsion with a hydrocarbon diluent; maintaining the resulting mixture in a settling zone, removing the emulsion when substantially free of solids and emulsified water from the top of the settling zone, withdrawing settled sludge from the bottom of the settling zone and centrifuging the withdrawn sludge to separate bitmen and diluent from the settled solids and the emulsified water.
U.S. Pat. No. 3,487,003 describes a method for reducing the solids content of an effluent discharge from a hot water process for separating oil from bituminous sands by adding a flocculating agent which may be organic inorganic or even a polyalkylene oxide of undisclosed molecular weight to this effluent; adjusting the pH of the effluent to less than 7.5 or more than 9 to effect flocculation of at least a portion of the solids therein; centrifuging the effluent now containing flocculated solids recovering the effluent discharge substantially reduced in solids content. This method treats not an oil-in-water emulsion but rather an effluent comprised of the effluent from the sand tailings layer and the middlings layer. Further, there is no appreciation therein of the necessity for maintaining the temperature within a given range during treatment with the flocculating agent.
Also generally known in the art is the concept of adding certain chemicals such as organic sequestering agents and organic flocculating agents to petroleum and other emulsions.
The cost of such chemicals amounting to around $1.00 to $1.30 per barrel of bitumen coupled with other operating and capital equipment costs precludes the obtaining of a final product which is economically equivalent to the cost of conventionally produced crude oil.